Edge diffraction and scattering in the early room impulse response

Although reverberation is a common and important measure of quality in architectural acoustics, the early part of a room’s impulse response is equally critical, as its spectrum and transient structure predominantly determine the initial filtering (i.e., the natural coloration) that a room endows on an (otherwise anechoic) source signal. Since this initial room filtering could make the difference between an acoustical impression that is, for example, either ‘‘clear and defined’’ or ‘‘murky and unfocused,’’ various studies have been performed to better understand and model the effects of edge diffraction and surface scattering on the early reflections in room impulse responses. These studies include auralizations with varying ‘‘diffusion’’ coefficients, computations and measurements of edge diffraction in early room impulse reponses, and application of ‘‘boss models’’ to compute hemispherical scattering in room acoustics auralization. Various results show that these effects can be clearly audible and that their audibility and perceived character depend on the input signal, among other factors. Conclusions are complemented with suggestions for future work. [Work supported by the Axson Johnson Foundation and Teknikbrostiftelsen, Sweden.]